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Semiconductor device and manufacturing method thereof

  • US 8,664,036 B2
  • Filed: 12/15/2010
  • Issued: 03/04/2014
  • Est. Priority Date: 12/18/2009
  • Status: Active Grant
First Claim
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1. A method for manufacturing a semiconductor device, comprising:

  • forming a first oxide semiconductor layer;

    performing first heat treatment on the first oxide semiconductor layer to form a crystal region which is grown from a surface toward an inside of the first oxide semiconductor layer, wherein the crystal region includes crystals whose c-axis is oriented in a direction substantially perpendicular to the surface of the first oxide semiconductor layer;

    forming a second oxide semiconductor layer over the first oxide semiconductor layer including the crystal region;

    performing second heat treatment on the first oxide semiconductor layer and the second oxide semiconductor layer in an atmosphere including oxygen at a constant temperature so as to form c-axis oriented crystals grown from the crystal region in the second oxide semiconductor layer and so as to supply oxygen to the first oxide semiconductor layer and the second oxide semiconductor layer;

    forming a conductive layer over the second oxide semiconductor layer on which the second heat treatment is performed;

    forming a source electrode layer and a drain electrode layer by selectively etching the conductive layer;

    forming an oxide insulating layer to cover the source electrode layer, the drain electrode layer, and the second oxide semiconductor layer, wherein the oxide insulating layer is in contact with the second oxide semiconductor layer;

    performing third heat treatment on the oxide insulating layer to supply oxygen to the second oxide semiconductor layer;

    forming a gate electrode layer over the oxide insulating layer, the gate electrode layer overlapping with the second oxide semiconductor layer to which oxygen is supplied;

    forming a nitride insulating layer including hydrogen over the gate electrode layer and the oxide insulating layer; and

    performing fourth heat treatment on the nitride insulating layer to terminate dangling bonds with hydrogen, the dangling bonds existing at least in the first oxide semiconductor layer and the second oxide semiconductor layer and at an interface between the second oxide semiconductor layer and the oxide insulating layer, wherein an oxygen concentration of the atmosphere is increased over heat treatment time in the second heat treatment.

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